Al—Mg—Mn weld filler alloys are known for use in large welded constructions which consist preferably of plates or extrusion members selected from the group of aluminium alloys of the AA5xxx-series. One of the standard weld filler alloys is the AA5183 alloy having the nominal composition, in weight %:
Mg4.3 to 5.2Mn0.5 to 1.0Zn0.25 max.Cr0.05 to 0.25Ti0.15 max.Fe0.40 max.Si0.40 max.Cu0.10 max.,
the balance substantially aluminium and incidental elements and impurities. AA5183 weld filler wire provides a good balance of high strength, corrosion resistance, bendability and weldability. By increasing the amount of magnesium in the alloy the strength of the weld joint can be increased. However, an increase in magnesium is usually accompanied by a decrease in corrosion resistance in this type of AlMg alloys.
Other disclosures such as JP-A-05169290 or GB-A-2000806 disclose weld filler alloys containing up to 6.0 weight % Mg up to 6.0 weight % Zn and up to 2.5 weight % Mn. The latter is disclosed in connection with a copper content of 0.2-0.5 weight %.
The proposed filler alloys are applied in welding techniques having a solidifying speed of higher than 1-3×102° C./s wherein Zr may be incorporated more than the quantity of the solid solution. The above mentioned British patent application thereby mentions copper as a compulsory element.
EP-1019217-B1 discloses an Al—Mg—Mn weld filler alloy comprising essentially the following composition (in weight %):
Mg5.0 to 6.5Mn0.4 to 1.2Zn0.4 to <2.0Zr0.05 to 0.3,
the balance essentially aluminium and incidental elements and impurities. The document discloses an improved strength compared with conventional AA5183 filler wire when welding a conventional AA5083 alloy plate under regular MIG welding conditions. The known weld filler alloy provides improved welded constructions with considerable improved corrosion resistance in the base material, the heat effected zone and the weld seam.